I suspect there is a bug in my Firefox browser's DNS, which is leading to some valid URLs being redirected to hostname '.com' on random occasions. This leads me to post a question on the Information Security site, which I thought was resolved by making some adjustment to the browser's configuration. But the problem resurfaces again today.
Since it happens only to my Firefox browser and not my Google Chrome browser, I believe it is a problem with the software and not some DNS hijacking. Further, I have no add-ons in the browser and clear my cache automatically upon closing the browser.
Note: I notice that I am not the only one facing this problem. In fact someone had flagged it up some six years ago. I want to know if there is a way to confirm my suspicion that Firefox is the culprit.